Final answer:
Covering the lower half of a lens results in a fainter image, as less light is collected to form the image, but the entire image is still generated. Option c is the correct answer.
Step-by-step explanation:
When discussing the effects of covering one part of a lens, especially the lower half, it's essential to understand how lenses form images. Despite a common misconception, a lens does not require its entire surface area to form an image.
Covering the lower half of the lens may lead to a reduction in the amount of light reaching the eye or detector, therefore, producing a fainter image. However, the entire image is still formed, indicating that all parts of a lens contribute to image formation.
So, the effect of covering the lower half of the lens is that the image remains the same, but its brightness or intensity may decrease. This outcome occurs because light rays from the object still pass through the upper half of the lens and continue to contribute to the image, which means that the lens has simply become less efficient in gathering light. Therefore, the correct option for what happens when the lower half of the lens is covered is: